This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A105397 #37 Aug 17 2020 22:44:17
%S A105397 4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,
%T A105397 4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,
%U A105397 4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2,4,2
%N A105397 Periodic with period 2: repeat [4,2].
%C A105397 A simple "Fractal Jump Sequence" (FJS). An FJS is a sequence of digits containing an infinite number of copies of itself. Modus operandi: underline the first digit "a" of such a sequence then jump over the next "a" digits and underline the digit "b" on which you land. Jump from there over the next "b" digits and underline the digit "c" on which you land. Etc. The "abc...n..." succession of underlined digits is the sequence itself.
%C A105397 Simple continued fraction of 2+sqrt(6). - _R. J. Mathar_, Nov 21 2011
%H A105397 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F A105397 a(n) = 3 + (-1)^n = 4 - 2*(n mod 2) = 2 * 2^((n+1) mod 2). - _Wesley Ivan Hurt_, Mar 14 2014
%p A105397 A105397:=n->3 + (-1)^n; seq(A105397(n), n=0..100); # _Wesley Ivan Hurt_, Mar 14 2014
%t A105397 Table[3 + (-1)^n, {n, 0, 100}] (* _Wesley Ivan Hurt_, Mar 14 2014 *)
%t A105397 LinearRecurrence[{0, 1},{4, 2},75] (* _Ray Chandler_, Aug 25 2015 *)
%o A105397 (PARI) contfrac(2+sqrt(6)) \\ _Michel Marcus_, Mar 18 2014
%Y A105397 Cf. A010694 (period 2, repeat [2,4]).
%Y A105397 First differences of A007310. - _Fred Daniel Kline_, Aug 17 2020
%K A105397 easy,nonn
%O A105397 0,1
%A A105397 _Eric Angelini_, May 01 2005
%E A105397 Edited by _N. J. A. Sloane_, Jun 08 2010